Seeing how most people who play M:tG leave the entire top line or top-right corner of their cards visible when holding their cards stack-style or fan-style; the fact that the same portion of the cards in your hand is visible for detailed identification of in-hand cards, indicates that card borders are of minor importance in the player's in-hand card identification for a card game designed from scratch.

Colour-coding cards isn't a guaranteed benefit for the player whose hand is holding the cards, and is going to be best for people who aren't the player. Looking over their shoulder to see what colour they're using. I really can't think of an example in a CCG where players use colour as the primary distinguishing between the cards in their hand; as opposed to say the actual name/cost of the card. Using colour as a distinguishing characteristic for in-hand cards also ignores the fact that many deck styles in CCGs tend to be mono-[faction/colour] for synergies, at which point using "colour" to "distinguish" in-hand cards seems nonsensical.

I'm not against colours as factions in games per se; it's just that the repeated posts of colour based factions keep proving that people aren't going to automatically have traction with any colour wheel that's thrown at them.

The system is all about creating factions; you could just as easily go with "North Star" & "Southron Cross" (i.e. the northern/southern hemispheres respective orientation constellations); or as complicated as a 16-point Rosicrusian star with (N; NNE, NE, ENE; E; ESE, SE, SSE; S; SSW, SW, WSW; W; WNW, NW, NNW) where the Cardinal points are considered "extremist"; the Primary InterCardinal points are considered "moderations" between; and the Half-Winds represent leanings towards one extreme or an other.

You can, but anyway you have to give an unique look and feel to each faction - in order to maximize the information conveyed by any part of the card. Seeing any small part of the card, you quickly identify the look and feel and the faction.

So yes, in the end your factions are forest, mountain, swamp, island and mountain, and that's how they are designated in the rules, but each of them has a corresponding color as part of the look and feel.

Color measurement is three dimensional. If we're describing them in terms of lightness and hue, the natural third dimension is saturation. Would there be any benefit to using that, as well, to differentiate similar colors?

For example: a slightly grey-green could make it more distinct from a more vibrant yellow and blue.

Color measurement is three dimensional. If we're describing them in terms of lightness and hue, the natural third dimension is saturation. Would there be any benefit to using that, as well, to differentiate similar colors?

For example: a slightly grey-green could make it more distinct from a more vibrant yellow and blue.

Saturation is too useful as an indicator of card type. One thing Magic does these days is to make colorless cards that are associated with a color have a low saturation of the appropriate color. So a red producing land will have a low saturation red bit on it, as does a red requiring devoid card.

Makes enough sense. So, use it for type among all colors, but not to differentiate colors.

But yeah, with varying lightness, if you alternated every color (light primaries and dark secondaries, or vice versa), that should be enough to make adjacent colors more distinct.

There's a couple things that are important. The first is that Red and Purple only have one neighbor because the spectrum is in fact a line and not a circle. The second thing to remember is that there are Colorblind people who are going to need help distinguishing Greens from Reds even though those are not adjacent spectrally.

Making green a dark pine green allows you to make Blue and Purple be very distinct by making the Purple a royal purple and the blue a bright cyan. But it also lets you distinguish the red from the green even if you have deuteranomaly.

One of the things that limits your number of colors is the existence of Booster Drafts and Sealed Decks. These days MtG makes packs that are 16 literal cards but only 14 playable cards. Which means that in a Booster Draft you end up selecting 42 cards after seeing 252 cards in an 8 person pod or 207 cards in a 6 person pod. This in turn means that pretty much everyone can make a typical draft deck in Magic because you only need to successfully end up with 22-24 cards in 2 colors plus colorless artifacts. Even if the draft has really gone to hell and you had to switch colors in pack two you should still have enough cards in your colors that you don't have to play bad cards. In a Sealed pool, you don't get the luxury of seeing cards passed by opponents, but you do get to open twice as many packs, so you have 84 cards to whittle down into a deck. Even if there's an even split among the colors, you're still looking at no less than 16 cards per color, so there should always be a two color combination that you could make that would have at least 8 cards to cut when making a deck.

It's important to note however how important the conceits of Magic are specifically to having that format work out. If limited required you to make a 60 card deck that wanted 36 playable non-land cards in it, that would be a complete non-started. Few draft or sealed decks could put together 36 on-color cards for a 2 color deck. If we were playing Hearthstone or Force of Will and no land cards went into the main deck, we wouldn't have enough cards to form a playable deck. If we mandated that all decks be one color instead of two, a significant fraction of sealed pools would have no legal playable deck and you'd have to be a draft super star to get enough cards to field a deck in draft.

What does this have to do with the number of colors? The more colors there are, the more strain there is on the limited format. With 5 colors, a sealed pool has a minimum of 16 cards in its best and second best color. With 6 colors, the minimum is a still-playable 14. With 7 colors, the minimum is a borderline un-playable 12. With 8 colors, the minimum is a literally unplayable 10. Note that the inclusion of playable neutral cards increases the average number of playable cards for a two color combination, but not the minimum. The existence of multi-colored cards decreases the minimum and the average. For a Magic-like game, the maximum number of colors that the limited formats as we play them today could handle is 6. And that's assuming we have a pretty Magic-like game, most especially that there are resource cards that we let people put in their deck from outside the packs and that players can freely mix and match 2 color-factions. Games like Force of Will, Shadowfist, Vampire, or L5R do not have satisfying booster draft formats at all.

Another consideration is that you're going to have to make a playable identity for each 2-color combination. Obviously, they aren't all going to be equally good at every table, and they won't all be equally good in abstract. But they should all be playable and they should all have a shtick. Sometimes Magic fails on this - in Battle For Zendikar the Green commons were just bad enough that all the Green/X color combinations had the identity of being "not very good" and in Kaladesh the Blue/Red combination was noted for being identityless and shit (despite having a truly excellent combo card, that people mostly played as a splash in Red/Green or Blue/Green decks). But it's obviously the goal you want to have.

For 5 colors, the number of 2 color combinations you are designing the set for is 10. For 6 colors, you are designing for 15 combinations. For 7 colors you are designing for 21 combinations (which is already kinda silly). And for 8 colors you are designing for a truly implausible 28 archetypes. To imagine how this works, let's imagine that your two-color archetypes are named after tribes, and for this example we'll do six colors with Purple Mountains, Red Moors, Orange Wastes, Yellow Plains, Green Forests, and Blue Swamps. This categorization uses a different one-letter code for each color and basic land type.

BG Fairies

BY Merfolk

BO Lizardfolk

BR Ghosts

BP Goblins

GY Elves

GO Bandits

GR Foulspawn

GP Elementals

YO Nomads

YR Rats

YP Dwarves

OR Zombies

OP Orcs

RP Demons

That's a workable set of tribes, though a few of them are just one flavor or another of beastmen or people with funny hats. But imagine how this works in a Draft. First of all, your set has to have support at common and uncommon for all 15 tribes, which is an enormous amount of the print sheet. For example, Kaladesh has 101 Common cards, so if each tribe got just 2 common cards in each color that it appeared in, that would be 60 out of 101 cards dedicated just to the themed cards, leaving just over forty percent for unthemed cards. Trying to do the same with 7 colors would require 84 on-theme common cards, which is literally too large for a small set like Aether Revolt (70 commons) to even contain. Even with six colors, the average number of each commons opened for each tribe in an 8-person pod is about 2.4 - so with only 4 on-theme commons for each two-color combination, a majority of draft decks are going to be more than half off-theme filler or random good stuff.

Note also the literal impossibility of filling out your curve with on-theme stuff in a draft deck. You're gonna need 2 drops, 3 drops, and 4 drops as well as removal and combat tricks, and your "on theme" commons can only fill four of those slots (and you are quite unlikely to get enough 2-cost cards from the on-theme portion even if you have a themed bear from both colors to draft - chances are there are only 4 or 5 of those cards at the whole table. As the only Merfolk drafter at the table there won't be enough Tide Lancers and Bog Singers for you to get such that you won't need to draft some random Yellow Nomad or Blue Fairy - and the fact that this is going to happen means you are also unlikely to get every single opened Tide Lancer and Bog Singer.

Now you can alleviate this issue somewhat by making some cards that have synergies with multiple archetypes. A good example is the Maulfist Squad from Kaladesh.

In Kaladesh, Black/White wants as many dudes on the table as it can get, Black/Green wants to put +1/+1 counters on things, and Black/Red wants random artifacts coming into play. So a dude that has the choice of coming into play with a +1/+1 counter or a little artifact dude is a pretty good dude for all three archetypes (in Kaladesh limited, Black/Blue is "bad"). But obviously you can only go so far with that sort of thing. If you print an Orange spell that both the Orcs and the Lizardfolk players want, it drops the average pull of that card for either player to a little over 1 if both Lizardfolk and Orcs are being drafted in the same pod. If there are three or more drafted archetypes hunting for a card, the average number each player gets is less than one and the impact is... limited.

Bottom line: the structure of drafting and the limitations of print sizes means that six colors is an upper limit of what can be supported in a set.

Note also that the themes of two color combinations don't have to be as blunt as tribal creatures. In Eldritch Moon the allied pairs were defined by creature tribes (ex.: Black/Red Vampirs or Green/Red Werewolves) while the opposite color pairs were defined by mechanics (ex.: Green/Black Delirium or Blue/Red Prowess). But of course, actually making all of those combinations be remotely playable is a challenge. Eldritch Moon Green/White was supposed to be a "humans" deck, but it ended up being "random stuff" and it won or lost based on its ability to play on-curve creatures and bombs and basically ignored the human theme it was supposed to have. It is, when all is said and done, rather hard to make a tribal blitz deck in Draft or Sealed, because you're always going to end up with some number of filler cards.

Or to put it another way, a synergy card that you want to play on Turn 4 is 25% more likely to appear at the correct time than a synergy card you want to play on turn 2. So if your gimmick is that you play an Emerge creature on top of a random creature with ETB or on-dies abilities on turn 4 or 5, that's a lot easier to pull off than if your gimmick is that you play a turn 2 creature that boosts your turn 3 creature. In Constructed, rarity mostly stops being a game mechanic and people correct for the fact that you have seen less cards when you are making early plays by packing more copies of cheap cards than expensive ones. So cheap synergy cards make a much bigger impact in Standard than they do in Draft. Example: the Winding Constrictor is format defining in G/B Energy and G/B Counters, but in Draft it's just "pretty good."

Another issue is that cards that are cheap are going to be fought over by people who aren't in your colors. That is to say, a random 2 drop Orc in Orange is going to be a high draft choice for any other Orange drafters, whether they are drafting OP Orcs or not. For a solid example, Black/White Go-Wide grabs up Dhund Operatives in Kaladesh drafts because they need 2-cost creatures and Dhund Operatives are pretty good. The fact that Dhund Operatives are a theme card for Black/Red Artifacts makes the Black/Red player want them more, but it doesn't stop Black/White players from taking them if they see the pack first.

I've been thinking about Limited a little more because there's a new Limited set. Let's assume that we have packs similar to Magic's packs - 15 cards with 11 uncommons, 3 uncommons, and 1 rare. That means that with 8 players at a draft table drafting cards, there will be:

264 Commons

72 Uncommons

24 Rares

I'm not counting mythics or secret rares or whatever the fuck as different because the average number of any particular rare opened at the table is going to be less than one. Assuming a Magic-like deck building paradigm, you're looking for 23 playable cards out of their final pick list of 45 with whatever special lands they are using not counting. This gives a fair amount of leeway for making bad cards (and you do need some bad cards for the good cards to be compared to) because there are 22 cards that people draft that don't get into their 23 spells. However:

Every time a player drafts something and then decides to change directions and play a different deck altogether that player has some very high picks that don't make the cut.

Every special land or mana accelerator or whatever the fuck that displaces one of the lands you'd add from outside the draft pool is something that makes your deck but also doesn't count as one of the 23.

Every card that's unplayable in your archetype (or so bad that it's just generally unplayable) is not going to make the cut.

Every time someone passes you a pack with all the cards from your colors and colorless removed, you're going to be stuck drafting a card you won't use.

Every card that is either worthless in Limited is going to eventually be drafted by someone and that is a dead card.

It's important to note that the colorless cards that are worth anything at all will go away in the first half of the pack, which means that when a pack comes around to you in the latter half of the draft that since two thirds of the cards are not in your color (for a six color wheel) that for pick 9 you are looking at 7 cards with a roughly 5.8% chance of seeing nothing in your colors, pick 10 you're looking at only 6 cards with an 8.8% chance of seeing nothing in your colors, pick 11 you see only 5 cards with a 13.2% chance of not seeing anything in your colors, pick 12 you see 4 cards with a 19.8% chance of seeing nothing in your colors, pick 13 you see only 3 cards and have a 29.7% chance of seeing nothing in your colors, with just 2 cards left you won't see your colors 44.4% of the time and the last card won't be a color you are interested in 67% of the time. So even if all the cards were playable in at least one of the decks at the table, you're still on average going to see about 2 cards that you have to take that you won't be able to play due to being off-color. More realistically, probably the last 2-3 cards are going to be ones no one really wants and you're going to end up stuck holding another one that's off color because one of the packs got drained of all the cards from the colors you are playing.

What this in turn means is that there is a number of cards that are going to be dead in your pool regardless of how many cards in the set are playable in the format. So honestly having some cards like Dubious Challenge and Lost Legacy that don't do jack shit in Limited is fine and having cards that are just plain unplayable like Protection of the Hekma are also fine. To a point, obviously people need to have playable cards in the packs they open. People can have about 3 to 4 genuinely worthless cards in each pack and still be able to make decks.

Now assuming there are something like 110 commons due to printing sheet sizes, the average number of each common in a draft pod is a little less than two and a half. Since each color is going to be being played an average of two and a half times, the average player is going to get only a single copy of a common that everyone in that color wants for their deck. And of course if your average is only 1, it's really easy to get less than average and just not have any copies at all. Which means of course that core cards for the curve need to have multiple near copies. Right now in Amonkhet, they made 3 turn 2 playable spells for each color, and that seems about right to me. And that would stay about right even if you went to 6 colors, meaning that the basic bear alotment would take up 18 slots on the printing sheet instead of 15.